An extruder head can have at least one pivotable head member rotatable about an axis, a stationary head member and, on each side of the extruder head, a hydraulic cylinder for clamping the pivotable head member to the stationary member to form the extrusion head.
In this known extruder head the individual head members are forced together into an operable unit by a side-mounted tension frame. The tension frame is acted on by hydraulic cylinders which are supported on or braced against the stationary central extruder head member. The tension frame has either two conical clamping surfaces (see, for example, German Open Patent Application No. 34 30 062) or hooklike clamps (see German Open Patent Application No. 17 29 618) which engage on the socalled brackets or short projections which are positioned on the sides on the pivotable head members.
In each case the tension frame must be laterally pivotable when the pivotable head members are to be raised or lowered to open the stock passage. However the lateral pivoting of the very wide tension frame requires considerable space. Moreover the hydraulic cylinder must, in as much as it must pivot with the pivoting frame (see German Open Patent Application No. 17 29 618), be connected by a flexible tube with a pressure source which causes considerable problems at the conventional high pressures of about 500 bar with the materials used for the apparatus.
A simple extruder head with two pivotable head halves is known as described in German Open Patent Application No. 24 57 532. The two extruder head halves have a joint plane of separation going through the axis of the extruder which is coincident with additional pressing surfaces on the front side of the extruder.
In this known extruder each hydraulic cylinder is pivotally connected centrally on top of and on the bottom of the cylinder of the screw extruder. Each hydraulic cylinder with its piston rod operates on a twin lever for release and clamping the magazine or housing and the shaping strip and acts to open, close and secure the head members. This closing system is limited to an extruder head with two pivotable head members which must pivot laterally for opening and closing of the head members, also for clamping the extruder head.